Author : Pisamai Chouvalitwongporn

Summary : Very low of potato tuber moth Phthorimaea operculella (Zeller) damage occurred in new seed storage. While in the warehouse where potato is continuously stored, there was a high percentage of damaged tubers (86.36 percent). Sex ratio (male to female) in the storage ranged from 1:0.75 to 1:1.55. Natural enemies of PTM were not found in the farmers' and Department of Agriculture storage areas. PTM larvae consumed an average of 0.22 grams of potato. At 15, 20, 30, and 35 degree C, PTM had low rate of development and there were only 1.0, 9.40, 10.21 and 4.35 degree C adult emergence, respectively. The fecundity at 20, 30 and 35 degree C were as low as 36.52, 32.65 and 1.35 eggs per female, respectively. While at 15 degree C, very few adults (only 2 males) emerged. In these temperatures, the net reproductive rate, the capacity of increase, and finite rate of increase were low compared to 25 degree C, controlled (23+2 degree C) and uncontrolled room (25-29 degree C) temperatures. The most suitable temperature for PTM development is 25 degree C. Among 8 Bt products evaluated, Centari, Baccut-P, Delfin and Bactac II were the most effective in reducing PTM population. Among these treatments, Delfin had the least cost. Hence, Delfin (Bacillus thuringiensis Berliner var kurstaki) at the rate of 10 g per 20 liters of water is recommended for the control of PTM in seed storage. The granulosis virus (GV 25 LE) at 25 larval equivalent per liter of water was effective in controlling PTM population. There were no significant differences between parasitization of 3 thrichogramma species to PTM and C. cephalonica eggs. Parasitization was 11.04-15.12 percent in PTM egg and 13.71-19.25 percent in C. cephalonica. While adult emergence was 83.93-93.87 percent and 86.86-89.28 percent in PTM and C. cephalonica eggs, respectively. Among these, T. nubilale was the most effective in parasitizing PTM eggs (32.41 percent). However, very low parasitization occurred in PTM eggs caged with these 3 trichogrammatids.